The invention relates to a unique card, for example, an identification or credit card, incorporating an image viewable as three-dimensional and a process of manufacturing the same.
Holograms are formed as an interference pattern between light from a coherent light source such as a laser reflected or transmitted through an object of interest and light from that same source serving as a reference beam. The pattern is recorded on a photographic plate which when illuminated by a coherent light source produces an image which is perceived as three-dimensional. While a true hologram can be viewed only in at least substantially coherent light, various techniques including multiplexing and the like can be used to create a modified interference pattern viewable in white light which retains its three-dimensional illusion.
Interference patterns of the latter type which are viewable in white light have been incorporated in credit and similar identification cards. Not only do the images provide a measure of security against counterfeiting, since production of such holograms requires considerably greater skill and knowledge than the printing technology well known to those skilled in these illegal arts, but perhaps most importantly the image provides an intrinsic advertising and promotional function. A corporate logo or symbol can be made to appear three-dimensional therefore creating an indelible image in the mind of the viewer. Typically, a small label less than one square inch is placed on one side of the card and bears a corporate logo or symbol.
Placement of the label on the card, however, has proved a difficult problem. One obvious approach is simply to attach the label after overlamination to one side of the card with a suitable adhesive. The difficulty with this approach is that the label can be removed and placed on another card even if strong adhesive is used so that the possibility of illegal use of a credit card still exists. Further, the label can be easily marred by normal use of the credit card.
However, incorporating such a label within the credit card is not simple. Typically, credit cards are formed by printing a blank of PVC with the desired information and then overlaminating on each side with a transparent layer. The sandwich thus formed is placed in an oven and heated until the overlaminating layers fuse to the blank. If a holographic label is formed of PVC material and incorporated in the sandwich, during heating the image will be lost as the raised portions of the PVC melt. Moreover, such labels for practical reasons must be quickly and efficiently positioned on the credit card blanks and mounted in place.
The present invention relates to a unique card and method of manufacturing the same in which the image viewable as three-dimensional is formed as a raised pattern on a sheet of material which is different from PVC. Heat sensitive adhesive is coated on each side of the label and each of the labels then applied to an individual PVC blank. Overlaminate transparent plastic layers are then conventionally fused to the blank. The label having a higher point of melting than PVC retains its raised pattern and image. The heat sensitive adhesive is triggered by the heat to form cross-molecular bonding between the PVC and the label. Preferably, a pressure sensitive adhesive taking up less than half the surface area of the label is provided on one side thereof to hold the label in position during overlaminating. The pressure adhesive material cannot take up the entirety of one side of the label since then no bonding could take place between that side of the label and the adjacent portion of the PVC blank.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings.